Transcript Document
Senior Project – Computer Engineering - 2005 Analog Communication over Wireless Networks By: Michael Pascucci Advisor: Professor Spinelli Purpose: -Voice-over-Internet-Protocol (VoIP) currently exists as a free telephone alternative. PCs connected over the Internet can access telephones using phone numbers converted to IP addresses. - My project allows for portable VoIP, using Microcontrollers (“cell phones”) connected over a wireless Internet network addresses. - Please note: Wireless RS-232 was used, not Wireless Internet Constraints: - Telephone Quality Audio ……~ Sample 8000 sample/sec (8 KHz) with 8 bits/sample ……~ Output at > 8 KHz (in 2n KHz increments) …… …… …… - Minimal Propagation Delay (< 200 ms) …… …… - Serial RS232 protocol-transmission …… ~ 115200 baud rate (bits/second) to prevent data loss …… …… … … ~ 8-n-1 transmission format (8 data bits, no parity, 1 start/stop bit) - 8 bit Analog-to-Digital Converter (ADC) / 12 bit Digital-to-Analog (DAC) Wireless VoIP Cell Phone Interpolating the signal on output allows a more accurate reproduction without increasing the input Sample Rate Input signal – 8 KHz sample rate Output signal – interpolation at 16 KHz Output signal – no interpolation Functional Diagram Analog voice to Digital System Schematic Dedicated Serial-to-Wireless Devices (replace with Serial-to-WiFi for use with the Internet) Digital to Analog voice Digital Data to Serial Port IP Packets from as IP Packets Serial Port to Digital Data Serial to Wireless Wireless to Serial To Internet From Internet Microcontrollers … Mic to ADC Headphone to DAC Mic to ADC Headphone to DAC